1. (Field of the Invention)
The present invention relates to a die-casting arrangement (method and apparatus) which is particularly useful for die-casting of aluminum alloy.
2. (Description of Prior Art)
In a prior art die-casting method, stationary and movable molds are parted from each other. A lubricant is then applied over a mold cavity surface, after which the stationary and movable molds are brought into contact with each other to form a mold cavity. Then molten metal is poured into an injection sleeve communicating with the mold cavity, and an injection plunger slidable in the injection sleeve is moved forward to inject molten metal from the injection sleeve into the mold cavity at high speed. Thereafter, the molten metal injected into the mold cavity solidifies during the lapse of a predetermined period of time. The resulting solidified article is ejected from the mold cavity by an ejector pin which is extended into the mold to force out the article.
However, this prior art die-casting method has functional problems. The lubricant applied to the movable and stationary molds becomes mixed with the molten metal while the molten metal is being injected into the mold cavity. Since the lubricant assumes a liquid or gaseous form during this mixing, the lubricant mixed in the molten metal may expand when the solidified article is later heated during use, thus causing the article to bulge.